1. Field of the Invention
This invention relates to solid electrolytic capacitors such as solid tantalum or aluminum capacitors. More specifically, the present invention relates to a solid electrolytic capacitor of the type which has two different built-in fuses for improving the safety of the capacitor.
2. Description of the Prior Art
It is generally known that a solid electrolytic capacitor such as tantalum capacitor provides a large capacitance while enabling a size reduction. On the other hand, the solid electrolytic capacitor is also known to generate a great amount of heat when the capacitor element has a certain defect or when the capacitor is erroneously incorporated in a circuit with reverse polarity.
In view of the above problem, it has been proposed to incorporate a temperature fuse wire in a solid electrolytic capacitor, as disclosed for example in "NEC Technical Report" Vol. 44, No. 10/1991, Pages 116-120. The temperature fuse, which may be typically made of a low melting point solder, is designed to thermally break when the temperature rises to an abnormal level of above 300.degree. C. for example.
Further, in an electric circuit incorporating a solid electrolytic capacitor, it is required to prevent various semiconductor components of the circuit from being damaged by an overcurrent which may be caused by a shorting for example. For this purpose, use may be made of an overcurrent fuse as an independent component, as disclosed in Japanese Utility Model Application Laid-open No. 59-141648 or Japanese Utility Model Publication No. 57-46615. Typically, the overcurrent fuse comprises a thin fuse wire made of a high melting point metal such as gold, copper or aluminum, and arranged between a pair of leads, the fuse wire being enclosed in a resin package.
However, since the prior art overcurrent fuse, which is an independent component, need be arranged separately, there is a limitation in increasing the packaging or mounting density (which is the number of electronic components per unit area) of a printed circuit board which incorporates the overcurrent fuse in addition to a solid electrolytic capacitor. Thus, a difficulty arises in reducing the size and weight of the printed circuit board. Further, the separate nature of the prior art overcurrent fuse necessitates separate mounting thereof by soldering, thereby increasing the production cost of the circuit board.